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Check Engine light, P1128

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The check engine light turned on when I was driving on the highway yesterday (2001 C2 Cab, 16K miles, one week after installing PSE exhaust). Stopped by my mechanic and he pulled one code out - P1128, which translates to "Oxygen Sensing Adaptation Area 2 (Cylinders 1 - 3) - Rich Threshold".

My mechanic reset the light and sent me on my way to see if it recurs. Any one have any experience with this (or suggestions)?

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P1128 Oxygen Sensing Adaptation Area 2 (Cylinders 1 - 3) - Rich Threshold

Fault condition: Fuel/air mixture is so lean that sensing has reached its rich threshold.

Translation: Oxygen sensing at rich threshold is stored in the memory, this means that the fuel/air mixture is too lean.

Air leaks ahead of the oxygen sensors can lead to a fault in adaptation also check exhaust system for leaks.

Fault area:

- Intake air system leaking.

- Fuel pressure too low.

- Volume supply of fuel pump too low.

- Fuel injectors fouled.

Start by checking for air or exhaust leaks - including the gas cap, oil filler cap, all hoses etc., etc.

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